MOS (metal oxide semiconductor) power transistors or MOS power devices which are commonly employed in automotive and industrial electronics, should have a low switch-on resistance (Ron), when being switched on. In a switch-off state, they should have a high breakdown voltage characteristic and withstand high source-drain voltages. For example, a MOS power transistor should withstand a drain to source voltage Vds in the order of tens or hundreds or thousands of volts when being switched off. As a further example, MOS power transistors conduct very large current which may be in the order of hundreds of Amperes at a gate-source voltage of about 2 to 20 V at a low voltage drop Vds.
Lateral MOS power devices, in which the current flow mainly takes place parallel to a first main surface of a semiconductor substrate, are commonly used. For example, lateral power devices are useful for integrated devices in which further components, such as switches, bridges and control circuits are integrated.
So-called TEDFETs have been developed in order to accomplish a power device having an increased on-current and a high breakdown voltage characteristic. TEDFETs specifically rely on the effect of accumulation in the drift region of a MOS power transistor.
In view of the above, there is a need of developing a lateral MOS power transistor which can be manufactured by a simple and cheap process.